function [ phi1,phi2,phi3,phi4] = dphi( alpha,beta)
%UNTITLED Summary of this function goes here
%   Detailed explanation goes here
lambda = 19e-2;
k=[cos(alpha)*cos(beta);cos(alpha)*sin(beta);sin(alpha)];
r1=[lambda/4,-lambda/4,0];
r2=[-lambda/4,-lambda/4,0];
r3=[-lambda/4,lambda/4,0];
r4=[lambda/4,lambda/4,0];
phi1=2*pi/lambda*(r1*k);
phi2=2*pi/lambda*(r2*k);
phi3=2*pi/lambda*(r3*k);
phi4=2*pi/lambda*(r4*k);
end

